Most current commercial mugs have a lining in them to prevent any leaching but still allows you to maintain the look and also the copper to help with temperatur

Most current commercial mugs have a lining in them to prevent any leaching but still allows you to maintain the look and also the copper to help with temperature. I can't find a quick reference but I read a while back that the drink, possibly the acid from the juice, reacted with the copper to add a flavour to the drink. With the lined mugs you don't get that specific taste.